Conventionally a record player has been known as having a turntable adapted to be rotatably supported through a center shaft provided at the center of the lower surface thereof. The shaft is rotatably supported through a bearing mechanism on a base plate of the player so that a smooth rotation of the turntable is ensured. In order to provide a high quality reproduction, it is necessary that the turntable be uniformly and constantly rotated without any off-center movement such as wow or flutter. To this end, the turntable has been designed in such a manner that it has a substantial weight with a uniform distribution of the weight throughout the turntable so that a high moment of inertia is provided. But, the conventional turntable cannot be made heavy enough to provide a very high inertia because the turntable is supported by only the center shaft.
Further, the presence of even a very slight gap between the center shaft of the turntable and the bearing mechanism will seriously affect the rotation of the turntable to cause irregular or non-uniform rotation. It therefore is required that the shaft and its bearing be precisely manufactured.
An air supported turntable assembly has been described in the U.S. Pat. No 3,479,038. The turntable described in the patent is floatingly supported by air which is introduced in the form of jets to an interface between the turntable and the base plate. Since the turntable is totally supported by air introduced through holes in the base, it is possible to increase the weight of the turntable as compared with that in the conventional arrangement. Such turntable having an increased weight can produce a high moment of inertia sufficient to ensure uniform and constant rotation of the turntable so that a high quality reproduction can be provided.
However, even in this type of turntable, it has been necessary that a center shaft be provided at the center of the lower surface of the turntable to rotate the turntable about the base plate. The shaft and the bearing mechanism are required to be precisely and accurately finished to avoid even slight irregularity or clearance. Precision manufacturing requires great skill in working and precision products are costly. Further, it is very difficult, or substantially impossible, to make a shaft and bearing which, when combined, are completely free from such an irregular clearance. In fact, it has been experienced that the turntable rotates with a small off-center movement. The off-center movement is preceived as undesired wow and flutter by the listener.